What do Dinesh D’Souza, Rod Blagojevich, and Martha Stewart have in common?

Yes, they’re at least mildly famous. (Blagojevich was even a contestant on Celebrity Apprentice.) All have been convicted of federal crimes. And they may be the beneficiaries of pardons from President Trump.

And that’s where things go from weird to very worrisome. Plainly Trump is not just using the pardon power as other presidents have, usually at the end of a term and typically to show mercy. Rather, Trump is doing it to send a clear signal to witnesses and prosecutors. Each of these miscreants were convicted of crimes that may have been committed by witnesses against Trump, or by the president himself.

Few expected a pardon for D’Souza, the conservative pundit. He was the incendiary journalist who pleaded guilty to a simple but serious campaign finance violation: funneling $20,000 through straw donors to evade campaign contribution limits. Blagojevich is serving time in federal prison as we speak. He was the Democratic governor of Illinois convicted of trying to sell off his appointment to fill Barack Obama’s Senate seat. A recording caught him saying, “I’ve got this thing, and it’s [expletive] golden. And I’m just not giving it up for [expletive] nothing.”

And Martha Stewart, of course, is the mega-successful lifestyle entrepreneur whose cookbooks, television show and magazines achieved canonical status in the 1980s and 1990s. She was convicted of lying to the FBI about the timing of an investment she made after receiving an inside tip. She spent five months in prison and has since become a criminal justice reform advocate. Campaign law violations. Public corruption. Lying to the FBI, even when the underlying conduct hadn’t been proved a crime. Now the pattern starts to become clearer. Can we think of anyone else who might have reason to worry about those particular misdeeds?

Trump’s pardons already have broken with longstanding practice followed by presidents of both parties. Most consult extensively with the federal pardon attorneys, and applicants go through an exhaustive process.

Trump started by pardoning Sherriff Joe Arpaio, a notorious supporter who was found guilty of contempt of court relating to civil rights violations. Presidents long stood behind federal courts, even when they disagreed with the rulings. Think of Dwight Eisenhower sending federal troops to Little Rock, Arkansas to enforce a federal ruling on school desegregation. Trump’s pardon of Arpaio sent a different message: if you are a supporter, I’ve got your back. No matter what.

Then he pardoned Scooter Libby, onetime chief of staff to Vice President Dick Cheney, convicted of lying during a leak investigation around the Iraq war. (The FBI chief when Libby lied was Robert Mueller.) George W. Bush had rejected the idea of pardoning Libby as he left office.

Both of these loomed as signals sent to possible witnesses in the ongoing investigation of Russian interference in the 2016 election. Trump and his defenders will say that he is taking a stand against the criminalization of politics. But there are far more ominous overtones.

These pardons semaphore wavering witnesses. They come as Michael Cohen, Paul Manafort and others must decide whether to cooperate with prosecutors. Just yesterday Trump’s former advisor Roger Stone vowed to the Daily Beast, “I will never roll on him!”

Of course, the specific crimes committed by these individuals may map the very charges that one could imagine being brought against Trump himself.

The overall message couldn’t be clearer: public corruption isn’t really a crime. And the pardon power is there to be used to make sure that nobody is truly held accountable.

His defenders note that the pardon power is in the Constitution. True. But a pardon that is given for improper reasons can still be a criminal act. When Bill Clinton pardoned fugitive financier Marc Rich as he was leaving office, a criminal investigation probed whether there was improper inducement. No charges were brought, but few Republicans then howled about the inviolate pardon power.

In fact, the articles of impeachment against Richard M. Nixon that were passed by the House Judiciary Committee in 1974 included a count charging Nixon with dangling clemency before the burglars.

When Trump’s lawyers discussed the pardons with Michael Flynn, they came dangerously close to outright obstruction of justice.

This is far subtler. None of these people are caught up in Trump’s metastasizing scandals. But their misconduct looks awfully familiar.

We’ve been lucky that so far, Trump has been hamfisted in his attempts to undermine the Russia probe and other investigations. Ominously, when it comes to abuse of power, he appears to be learning on the job.